At the stroke of midnight an eerie cry that has echoed through more than four centuries is said to be heard in the heart of Mexico City.

The mournful voice is that of a grief-striken women,who wails: 'Oh, my children, my pitiful, wretched children.' She is La Llorona, the Wailing Women. Wearing a torn and blood-stained gown, she haunts the night, wailing her grief.

According to Mexican legend, dating back to 1550, the voice belongs to Doña Luisa de Olveros, a Spanish-Indian of outstanding beauty, who took as her lover a nobleman, Don Nuño de Montesclaros. She bore him two children, loved him deeply and prayed for the day when she would become his bride.

But Don Nuño did not return her feelings and, once his passion had died, began to neglect her. Lonely and puzzled, Luisa finally decided one night to walk to the palatial home of the wealthy and influential Monteclaros family in the hope of seeing her lover and begging him to come back. She found him - but to her horror he was in the centre of a lavish party, celebrating his marriage that day to a spanish noblewoman.

Luisa rushed to him in tears, but he pushed her away, coldly telling her that because of her Indian blood she was unacceptable and could never have become his wife.

Hysterical, she ran home to her children and killed them with a small dagger which had been a present from her lover. She fled from the house, covered with her children's blood and dashed through the streets screeming, until she was arrested and thrown into prison. She was convicted of sorcery.

Doña Luisa de Olveros was publicly hanged in Mexico City and, as a final humiliation, her body was left swinging in 'public mockery' for six hours. Every night since then, her ghostly cries have rung out and will continue to, so the legend says, until the end of time.